|Publication number||US5379333 A|
|Application number||US 08/155,037|
|Publication date||Jan 3, 1995|
|Filing date||Nov 19, 1993|
|Priority date||Nov 19, 1993|
|Publication number||08155037, 155037, US 5379333 A, US 5379333A, US-A-5379333, US5379333 A, US5379333A|
|Inventors||Thomas L. Toth|
|Original Assignee||General Electric Company|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (2), Non-Patent Citations (2), Referenced by (163), Classifications (16), Legal Events (4)|
|External Links: USPTO, USPTO Assignment, Espacenet|
The present invention relates to computed tomography (CT) imaging apparatus; and more particularly, to reducing the x-ray dose applied to a patient without significantly increasing noise artifacts in the image.
In a computed tomography system, an x-ray source projects a fan-shaped beam which is collimated to lie within an X-Y plane of a Cartesian coordinate system, termed the "imaging plane." The x-ray beam passes through the object being imaged, such as a medical patient, and impinges upon an array of radiation detectors. The intensity of the transmitted radiation is dependent upon the attenuation of the x-ray beam by the object and each detector produces a separate electrical signal that is a measurement of the beam attenuation. The attenuation measurements from all the detectors are acquired separately to produce the transmission profile.
The source and detector array in a conventional CT system are rotated on a gantry within the imaging plane and around the object so that the angle at which the x-ray beam intersects the object constantly changes. A group of x-ray attenuation measurements from the detector array at a given angle is referred to as a "view" and a "scan" of the object comprises a set of views made at different angular orientations during one revolution of the x-ray source and detector. In a 2D scan, data is processed to construct an image that corresponds to a two dimensional slice taken through the object. The prevailing method for reconstructing an image from 2D data is referred to in the art as the filtered backprojection technique. This process converts the attenuation measurements from a scan into integers called "CT numbers" or "Hounsfield units", which are used to control the brightness of a corresponding pixel on a cathode ray tube display.
Quantum noise degrades the diagnostic quality of a CT image and this noise is related to the amount of x-rays, or "dose", employed to acquire the attenuation measurements, and to the attenuation characteristics of the patient. Image artifacts due to noise will increase if the x-rays measured at the detector drop to low levels either because the prescribed x-ray dose is too low or the beam is highly attenuated by patient anatomy. The x-ray dose is controlled by the filament current ("mA") applied to the x-ray tube, and the practice is to fix this current at a level which provides a constant dose during the entire scan. If the operator prescribes a high dose, image quality is superb throughout, but excessive x-ray flux is produced during portions of the scan when patient attenuation is low. The patient is thus exposed to an excessive dose and the x-ray tube is unnecessarily heated. On the other hand, if the dose is reduced (to prevent tube overheating during the prescribed scan), noise artifacts will appear in the image oriented at locations where the beam is highly attenuated. For example, horizontal streaks may appear in slices through a patient' s shoulders and hips.
The present invention relates to a CT imaging system in which the x-ray dose is modulated as the gantry is rotated during a scan such that a prescribed noise level is better maintained in all of the acquired attenuation measurements. More specifically, a modulation profile which is indicative of the variations in patient attenuation during a revolution of the gantry is employed during the scan to modulate x-ray tube current as a function of gantry rotation to dynamically scale the dose as required by the patient's anatomy. In one implementation, a modulation profile is stored for imaging specific human anatomy (such as the eyes), and in another implementation the modulation profile is constructed from a general purpose modulation template which is "tailored" to the patient's particular anatomy using attenuation data acquired with a "scout" scan.
A general object of the invention is to minimize the x-ray dose applied to a patient while maintaining a prescribed small noise increase in the reconstructed image. The values in the modulation profile reflect the expected attenuation of the x-ray beam at all gantry angles, and they modulate the tube current (mA) such that attenuation measurements are obtained at a desired noise level throughout the scan. As a result, the dose may be substantially reduced at some gantry angles where patient attenuation is low. For example, consider a scan through the patient's hips where the dose is kept constant for a horizontal view (highly attenuated) and a vertical view (low attenuation). If the noise figure for the highly attenuated view is 10, the noise figure for the other view may only be 1. A characteristic of CT is that these noise figures add as the square root of the sum of the squares (i.e. (102 +12)1/2), such that the low noise view contributes minimally to the total noise figure and to image artifacts. This is why image artifacts typically appear as streaks in the direction of the highly attenuated views. Doubling the smaller noise figure in this example by substantially cutting the x-ray dose at vertical gantry positions only increases the total noise by 1.5%. Since noise increases of less than 5% generally cannot be seen in the reconstructed image by radiologists, this affords ample opportunity to reduce x-ray dose over a wide range of gantry angles at many slice locations.
Another object of the invention is to reduce the x-ray exposure of specific portions of the patient without significantly increasing image noise. Some organs, such as the eyes, are particularly sensitive to ionizing radiation. By modulating the beam intensity as a function of gantry angle such that the dose is reduced at the gantry angles in which the eyes are directly exposed to the x-ray source, the total dose to the eyes is reduced. To maintain noise within prescribed limits, the beam intensity is increased for opposing views in which the x-ray source is rotated behind the patient's head. The modulation profile for such a scan is shown in FIG. 3.
Another object of the invention is to automatically generate a modulation profile for use in scanning a patient with minimal dose and a clinically insignificant noise increase. A transverse slice through a patient may be viewed radiologically as an oval shape having major and minor axes which change along the length of the patient. For example, at the hips the major axis is horizontal and muck longer than the vertical minor axis, whereas at the neck, the major axis is vertical and only a little longer than the minor axis. At other locations the radiological profile may be nearly circular. A general purpose modulation template having a substantially sinusoidal shape at twice the frequency of the gantry rotation may be automatically tailored to such radiological profiles by acquiring two orthogonal views through the transverse slice prior to the scan. This "patient projection" data is analyzed to locate the major and PG,6 minor axes of the oval and determine their relative lengths. This information is employed to produce a modulation profile from the sinusoidal template. Such a modulation profile is shown in FIG. 4 for a slice having a horizontal major axis substantially greater than a vertical minor axis. This will reduce tube current (mA) to 50% of its prescribed amount as the x-ray source rotates above and below the patient. For a slice with less difference between the major and minor axes, the tube current would be reduced by less than 50%.
A more specific object of the invention is to alter the shape of the modulation profile when the x-ray source cannot be modulated enough to reduce the dose. The ability of the x-ray tube and its filament current supply to respond to the modulation profile may be limited. For example, a 50% modulation may be the limit. It is a teaching of the present invention that the shape of the modulation profile can be changed when the modulation limit is exceeded to recapture some benefit of the desired lower dose level.
FIG. 1 is a pictorial view of a CT imaging system in which the present invention may be employed;
FIG. 2 is a block schematic diagram of the CT imaging system;
FIG. 3 is a graphic representation of a modulation profile for scanning a patient's head with reduced x-ray dose to the eyes;
FIG. 4 is a graphic representation of a sinusoidal modulation profile employed in the preferred embodiment of the invention;
FIG. 5 is a flow chart of a program executed by the CT imaging system of FIG. 2 to carry out the preferred embodiment of the invention; and
FIGS. 6A and 6B are schematic representations of exemplary scout data acquired at two locations in a patient.
With initial reference to FIGS. 1 and 2, a computed tomography (CT) imaging system 10 includes a gantry 12 representative of a "third generation" CT scanner. Gantry 12 has an x-ray source 13 that projects a beam of x-rays 14 toward a detector array 16 on the opposite side of the gantry. The detector array 16 is formed by a number of detector elements 18 which together sense the projected x-rays that pass through a medical patient 15. Each detector element 18 produces an electrical signal that represents the intensity of an impinging x-ray beam and hence the attenuation of the beam as it passes through the patient. During a scan to acquire x-ray projection data, the gantry 12 and the components mounted thereon rotate about a center of rotation 19 located within the patient 15. A reference detector at one end of the array 16 measures the unattenuated beam intensity during the scan to detect variations in the applied x-ray dose. This reference data is used in subsequent processing of the x-ray projection data to normalize it to a common reference dose.
The rotation of the gantry and the operation of the x-ray source 13 are governed by a control mechanism 20 of the CT system. The control mechanism 20 includes an x-ray controller 22 that provides power and timing signals to the x-ray source 13 and a gantry motor controller 23 that controls the rotational speed and position of the gantry 12. A data acquisition system (DAS) 24 in the control mechanism 20 samples analog data from detector elements 18 and converts the data to digital signals for subsequent processing. An image reconstructor 25, receives sampled and digitized x-ray data from the DAS 24 and performs high speed image reconstruction. The reconstructed image is applied as an input to a computer 26 which stores the image in a mass storage device 29.
The computer 26 also receives con, hands and scanning parameters from an operator via console 30 that has a keyboard. An associated cathode ray tube display 32 allows the operator to observe the reconstructed image and other data from the computer 26. The operator supplied commands and parameters are used by the computer 26 to provide control signals and information to the DAS 24, the x-ray controller 22 and the gantry motor controller 23. In addition, computes 26 operates a table motor controller 34 which controls a motorized table 36 to position the patient 15 in the gantry 12.
Referring particularly to FIG. 2, the computer 26 directs the system components to carry out the prescribed scan in accordance with stored programs. If an mA modulation strategy is selected by the operator, the program illustrated by the flow chart in FIG. 5 is executed by computer 26 to implement the preferred embodiment of the present invention. The first step is to acquire scout data, as indicated at process block 110. This scout data is comprised of two orthogonal views from each slice in the prescribed scan, one at a gantry angle of 0° and the other at an angle of 90°. The next step, as indicated at process block 111, is to calculate the maximum x-ray tube current (mAmax) for each slice using the scout data as described in copending U.S. patent application Ser. No. 08/155,045 filed on even data herewith and entitled "Dynamic Dose Control In Multi-Slice CT Scan." This enables the x-ray dose to be reduced for slices with reduced attenuation of the x-ray beam without exceeding the prescribed image noise. It results in an array of stored values (mAmax), one for each of the respective slices in the scan.
As indicated at decision block 112, the operator is then signalled to indicate if automatic modulation is to be applied during the scan, and if so, a flag is set at process block 113 and a modulation index (α) is calculated for each slice as indicated at process block 114. As described in detail below, the modulation index (α) is calculated from the scout data and it indicates the degree to which x-ray tube current can be modulated without significantly increasing noise artifacts in the reconstructed image. This modulation index is used to produce a modulation profile as will also be described below.
If the automatic mode is not selected, the system branches at decision block 112 and the scout data is employed to produce an image for the operator at process block 115. This image enables the operator to locate the prescribed slices with respect to the patient's anatomy and to manually select appropriate x-ray tube current modulation profiles at process block 116. For example, the operator may choose special purpose modulation profiles such as that shown in FIG. 3 for those slices intersecting the patient's eyes. This particular profile reduces tube current while the x-ray tube is above the patient to thereby reduce the x-ray dose applied directly to the eyes. To compensate for this lower dose without increasing image noise, the x-ray tube current is increased above the prescribed amount when the gantry revolves the x-ray source to the back of the patient's head. In the preferred embodiment, this and other modulation profiles are stored as twenty values which, when multiplied by the maximum tube current (mAmax) calculated above, provide twenty current commands for the x-ray controller 22 that determine x-ray tube current at twenty successive 18° segments of gantry revolution.
Referring still to FIGS. 2 and 5, regardless of the modulation profile selected, the computer 26 starts the scan at process block 120, by signaling the gantry motor controller 23. It then enters a loop in which the twenty mA commands are calculated at process block 121 and downloaded to the x-ray controller 22. When the auto mode has been selected, this step involves the application of the modulation index (α) calculated above and the maximum current (mAmax) also calculated above to a general purpose sinusoidal template expressed as follows: ##EQU1## where: mAmax =the tube current without modulation,
α=modulation index calculated from the scout data;
wt=gantry angle (θ) at time t, and
φ=starting phase in the sinusoidal template determined from the scout data.
In the manual mode, the calculation of the twenty mA commands requires multiplication of the maximum current (mAmax) by the twenty stored modulation profile values. Regardless of the mode, at process block 122 the twenty mA values are downloaded to the x-ray controller 22 and a timing signal is sent to coordinate the start of the dose with gantry orientation and table position.
As each slice is acquired the gantry 12 is rotated at a constant angular rate by the gantry motor controller 23. At the completion of each 18° increment of gantry rotation the next mA current command downloaded to the x-ray controller 22 is read out and used to control x-ray tube filament current during the next 18° increment of rotation. This cycle continues until all twenty mA current commands have been applied in succession as the gantry completes a 360° rotation.
The cycle of calculating mA current commands and downloading them to the x-ray controller 22 continues until the last slice in the prescribed scan is acquired as detected at decision block 123. The gantry is then stopped at process block 124 and the operator is signaled that the scan is finished.
The acquired x-ray profile data is processed in the usual fashion to reconstruct a slice image. Even though the views are acquired with varying x-ray beam intensity, the data is normalized with the reference detector signal as mentioned above so that the reconstruction of the image is performed with x-ray profile data that is effectively acquired with a constant x-ray beam intensity during the entire gantry revolution.
The acquisition of scout data is required to implement the automatic dose modulation mode described above. To accomplish this, the patient table 36 is moved and the gantry is rotated to acquire attenuation data for two orthogonal views in each slice to be imaged. In the preferred embodiment, gantry angles of 0° and 90° are chosen for the scout data:
S0 (i,z) and S90 (i,z)
i=detector channel number; and
z=location of slice along z axis.
As shown in FIG. 6A, when the slice intersects the patient's shoulders the signal S0 (i,z) is attenuated very much less than the signal S90 (i,z) because the attenuation profile 130 at this point in the human anatomy is much wider than it is high. As shown in FIG. 6B, however, when the scout slice intersects the patient's neck the signal S0 (i,z) is attenuated more than the signal S90 (i,z) because the attenuation profile 131 is narrower than it is high. The scout data is analyzed to detect these differences in attenuation profiles so that the values of α and φ required by the general purpose sinusoidal template described above in equation (1) may be calculated. These are determined from the scout data as follows. First, offset corrections are made to each channel (i) of the raw data received from the DAS 24.
S0 (i,z)=S0 (i,z)-offsets (i)
S90 (i,z)=S90 (i,z)-offsets (i)
This corrected data is then convolved along the z axis with a 10 point low pass filter F(z) and the filtered data is resampled at each 5 mm slice in the scan. The filtered scout data in each slice is then low pass filtered in i by finding the average value in each of five 70 channel regions centered on the isocenter. These five central regions are indicated at 132 and 133 in FIG. 6A. For each slice the minimum average value min0 (z) from the five 0° regions and the minimum average value min90 (z) from the five 90° regions are found. The modulation index α and phase φ are a function of the patient attenuation ratio and are calculated as follows: ##EQU2##
A table of modulation indices (α) vs attenuation ratios can be generated empirically to produce a small known amount of noise increase in the image (i.e., 5%). As the patient attenuation ratio increases, the image noise decreases, and thus the % modulation can be increased to further decrease patient dose without exceeding the 5% image noise limit. The table is fixed and need be computed only once and is provided as part of the system software. In the preferred embodiment of the invention a table with the following eight entries is used.
______________________________________ ratio α______________________________________ 1.0 0.0 1.5 .1 2.9 .2 6.3 .25 14.9 .33 28.7 .44 60 .60 133 .75______________________________________
During patient scanning, the attenuation ratio determines the index into this table (which can be linearly interpolated between entries) to produce the proper modulation index (α).
These values are employed in equation (1) above to calculate the twenty current commands (mA) at successive 18° (i.e. 2π/20 radians) gantry angles (θ) which comprise the modulation profile. Such a modulation profile is illustrated by the solid line 140 in FIG. 4, where the modulation index (α) is approximately 0.5. For slices passing through patient attenuation profiles that are more circular, the value of α is less and the sinusoidal modulation of the current commands mA in FIG. 4 are reduced. On the other hand, when the measured patient attenuation profile becomes very oblong, the modulation index (α) becomes larger and the sinusoidal modulation of the current commands mA becomes greater.
At some point, it may not be possible to further increase modulation to achieve further dose reduction because of limitations inherent in the X-ray tube and generator. If the dose cannot be modulated by the full amount indicated by the scout data, the shape of the sinusoidal template can be changed to realize at least a portion of the dose savings. This is illustrated by the dashed line 141 in FIG. 4 for the situation in which a modulation index greater than 0.5 cannot be achieved and the template shape is changed to increase the width of the low mA duty cycle.
The patient attenuation ratio is predetermined at the point where the dashed waveform 141 in FIG. 4, with a 0.5 modulation index, produces a 5% image noise increase. This occurs at a higher patient attenuation ratio than for the solid waveform 140 in FIG. 4. Between the attenuation ratios for maximum modulation of the solid waveform 140 and the dashed waveform 141, the waveform shape is linearly interpolated. Thus, the dose savings can be increased beyond the solid waveform 140 to the maximum provided by the dashed waveform 141. The dashed waveform 141 would not be used for lower attenuation ratios since it is less efficient and would produce higher patient dose for the same image noise increase than the solid waveform 140 at these attenuation ratios.
It should be apparent to those skilled in the art that many modifications can be made to the preferred embodiment described herein without departing from the spirit of the invention. For example, other preset modulation profiles may be stored and presented to the operator for use during the scan. Also, while the sinusoidal shape at twice the gantry frequency is preferred as the general purpose template, other shapes are possible. Also, while the patient projection data is obtained in a scout scan in which views are acquired at gantry angles of 0° and 90° in the preferred embodiment, different angles can be used and more scout views can be acquired to gather the patient attenuation profile information. Also, the patient projection data may be acquired in a helical survey scan or from an adjacent slice which has already been acquired. It should also be apparent that the present invention is applicable to a CT system which acquires each slice either while the patient table is stationary or in a spiral scan in which the table is moved continuously throughout the data acquisition.
|Cited Patent||Filing date||Publication date||Applicant||Title|
|US4624007 *||Feb 22, 1984||Nov 18, 1986||Tokyo Shibaura Denki Kabushiki Kaisha||Method of obtaining X-ray CT image and apparatus for utilizing the same method|
|US5103469 *||Feb 28, 1991||Apr 7, 1992||Kabushiki Kaisha Toshiba||X-ray CT scanner|
|1||U.S. patent application Ser. No. 854,227, filed May 19, 1986 and entitled "Dynamic Flux Intensity Control In Computer Tomography Systems".|
|2||*||U.S. patent application Ser. No. 854,227, filed May 19, 1986 and entitled Dynamic Flux Intensity Control In Computer Tomography Systems .|
|Citing Patent||Filing date||Publication date||Applicant||Title|
|US5450462 *||Sep 6, 1994||Sep 12, 1995||General Electric Company||Modulation of x-ray tube current during CT scanning with modulation limit|
|US5485494 *||Aug 3, 1994||Jan 16, 1996||General Electric Company||Modulation of X-ray tube current during CT scanning|
|US5608775 *||Sep 29, 1995||Mar 4, 1997||Siemens Aktiengesellschaft||X-ray diagnostic installation having a solid-state image converter and method for operating same|
|US5625662 *||Nov 20, 1995||Apr 29, 1997||General Electric Company||Modulating x-ray tube current in a CT system|
|US5629971 *||May 11, 1995||May 13, 1997||Adac Laboratories||Scan speed for transmission exposure reduction in a nuclear medicine camera|
|US5822393 *||Apr 1, 1997||Oct 13, 1998||Siemens Aktiengesellschaft||Method for adaptively modulating the power level of an x-ray tube of a computer tomography (CT) system|
|US5867555 *||Mar 4, 1997||Feb 2, 1999||Siemens Aktiengesellschaft||Adaptive dose modulation during CT scanning|
|US5873826 *||Jul 11, 1997||Feb 23, 1999||Ge Yokogawa Medical Systems, Limited||Fluoroscopy method and X-ray CT apparatus|
|US6038283 *||Oct 24, 1997||Mar 14, 2000||Nomos Corporation||Planning method and apparatus for radiation dosimetry|
|US6067341 *||Sep 22, 1998||May 23, 2000||Ge Yokogawa Medical Systems, Limited||X-ray computed tomography method and apparatus|
|US6094468 *||Jun 24, 1998||Jul 25, 2000||U.S. Philips Corporation||Adjustable computer tomography device|
|US6185271||Feb 16, 1999||Feb 6, 2001||Richard Estyn Kinsinger||Helical computed tomography with feedback scan control|
|US6198789||Jan 26, 1998||Mar 6, 2001||Marconi Medical Systems Israel Ltd.||Variable current CT scanning|
|US6289075 *||Oct 25, 1999||Sep 11, 2001||Shimadzu Corporation||X-ray CT apparatus|
|US6307912||Nov 29, 1999||Oct 23, 2001||General Electric Company||Methods and apparatus for optimizing CT image quality with optimized data acquisition|
|US6385280||Aug 6, 1999||May 7, 2002||Siemens Aktiengesellschaft||X-ray computed tomography apparatus with modulation of the x-ray power of the x-ray source|
|US6393096||May 27, 1999||May 21, 2002||Nomos Corporation||Planning method and apparatus for radiation dosimetry|
|US6404844 *||Nov 21, 2000||Jun 11, 2002||Ge Medical Systems Global Technology Company, Llc||Tomographic imaging scan condition determining method, tomographic imaging method and X-ray CT apparatus|
|US6507639||Aug 30, 2001||Jan 14, 2003||Siemens Aktiengesellschaft||Method and apparatus for modulating the radiation dose from x-ray tube|
|US6560309||Nov 28, 2000||May 6, 2003||Siemens Aktiengesellschaft||Method for examining a body region executing a periodic motion|
|US6754301 *||Aug 27, 2002||Jun 22, 2004||Ge Medical Systems Global Technology Company, Llc||X-ray CT system, gantry apparatus and operation console|
|US6775352||Aug 16, 2002||Aug 10, 2004||Ge Medical Systems Global Technology Company, Llc||Method and system for implementing variable x-ray intensity modulation schemes for imaging systems|
|US6795528 *||Jan 4, 2002||Sep 21, 2004||Canon Kabushiki Kaisha||Radiographic apparatus, radiographic method, and computer-readable storage medium|
|US6850588 *||Jul 25, 2002||Feb 1, 2005||Ge Medical Systems Global Technology Company, Llc||Radiation exposure limiting scheme|
|US6904127||Nov 21, 2001||Jun 7, 2005||General Electric Company||System and method of medical imaging having default noise index override capability|
|US6954513||Dec 17, 2003||Oct 11, 2005||Ge Medical Systems Global Technology Company, Llc||X-ray CT Apparatus and exposure dose calculating method|
|US6956929||Sep 11, 2003||Oct 18, 2005||Siemens Aktiengesellschaft||Method for controlling modulation of X-ray tube current using a single topogram|
|US6987828 *||Mar 25, 2003||Jan 17, 2006||Ge Medical Systems Global Technology Company, Llc||Transmitted X-ray data acquisition system and X-ray computed tomography system|
|US6990171||Jan 27, 2004||Jan 24, 2006||General Electric Company||System and method of determining a user-defined region-of-interest of an imaging subject for x-ray flux management control|
|US6990172||Feb 19, 2004||Jan 24, 2006||General Electric Company||Method and apparatus to determine tube current modulation profile for radiographic imaging|
|US7068750||Jan 27, 2004||Jun 27, 2006||General Electric Company||System and method of x-ray flux management control|
|US7068751||Jan 27, 2004||Jun 27, 2006||General Electric Company||System and method of determining a center of mass of an imaging subject for x-ray flux management control|
|US7142630||Apr 18, 2005||Nov 28, 2006||Kabushiki Kaisha Toshiba||X-ray computed tomography apparatus with X-ray intensity control|
|US7158611 *||Aug 21, 2002||Jan 2, 2007||Siemens Aktiengesellschaft||Method for determining density distributions and atomic number distributions during radiographic examination methods|
|US7260182||May 23, 2006||Aug 21, 2007||General Electric Company||Method and apparatus of radiographic imaging with an energy beam tailored for a subject to be scanned|
|US7277523||May 28, 2004||Oct 2, 2007||Koninklijke Philips Electronics, N.V.||Contour and scout scanning technique for pulsed x-ray large area CT detectors|
|US7289596||Jul 12, 2006||Oct 30, 2007||Ge Medical Systems Global Technology Company, Llc||Radiation tomography apparatus and scan condition setting device|
|US7313217||Jan 27, 2004||Dec 25, 2007||General Electric Company||System and method of collecting imaging subject positioning information for x-ray flux control|
|US7336762 *||Jul 12, 2005||Feb 26, 2008||Ge Medical Systems Global Technology Company, Llc||Scan program communication method and X-ray CT apparatus|
|US7502439||Jun 26, 2006||Mar 10, 2009||Ge Medical Systems Global Technology Company, Llc||Radiographic apparatus and method of using the same|
|US7558365||Jun 20, 2008||Jul 7, 2009||Ge Medical Systems Global Technology Company, Llc||Scanning detection device of an X-ray CT apparatus, an X-ray CT system, and method of operation of the same|
|US7630477||Jul 31, 2007||Dec 8, 2009||General Electric Company||Method and apparatus of radiographic imaging with an energy beam tailored for a subject to be scanned|
|US7636416 *||Feb 27, 2006||Dec 22, 2009||Hitachi Medical Corporation||X-ray CT apparatus comprising a tube current control unit|
|US7636422||Dec 23, 2008||Dec 22, 2009||Ge Medical Systems Global Technology Company, Llc||X-ray CT apparatus and X-ray tube current determining method|
|US7639776 *||Dec 29, 2009||Ge Medical Systems Global Technology Company, Llc||X-ray CT apparatus|
|US7688938||Jan 22, 2007||Mar 30, 2010||Wisconsin Alumni Research Foundation||Method and apparatus for low dose computed tomography|
|US7693252 *||Apr 6, 2010||Kabushiki Kaisha Toshiba||Medical image display apparatus and medical image display system|
|US7756243 *||Nov 30, 2005||Jul 13, 2010||Ge Medical Systems Global Technology Company, Llc||Dose evaluating method and X-ray CT apparatus|
|US7760849 *||Jul 20, 2010||William Beaumont Hospital||Tetrahedron beam computed tomography|
|US7873144 *||Dec 5, 2005||Jan 18, 2011||Koninklijke Philips Electronics N.V.||Pulsed x-ray for continuous detector correction|
|US7912176 *||Sep 15, 2008||Mar 22, 2011||Siemens Medical Solutions Usa, Inc.||Dose-sparing tomographic imaging|
|US7927313||May 27, 2004||Apr 19, 2011||Baxter International Inc.||Medical device configuration based on recognition of identification information|
|US7983457 *||Nov 23, 2005||Jul 19, 2011||General Electric Company||Method and system for automatically determining regions in a scanned object|
|US7995703 *||Aug 9, 2011||Ge Medical Systems Global Technology Company, Llc||Method for controlling X-ray exposure in X-ray CT system|
|US8031831 *||Oct 4, 2011||Kabushiki Kaisha Toshiba||Voltage and or current modulation in dual energy computed tomography|
|US8611490||Jun 29, 2010||Dec 17, 2013||William Beaumont Hospital||Tetrahedron beam computed tomography|
|US8670523||Jan 4, 2011||Mar 11, 2014||William Beaumont Hospital||Intensity modulated arc therapy with continuous couch rotation/shift and simultaneous cone beam imaging|
|US8712121||Jun 23, 2009||Apr 29, 2014||Koninklijke Philips N.V.||Image generation device with optimized dose control|
|US8744039 *||Jun 29, 2009||Jun 3, 2014||Hitachi Medical Corporation||X-ray CT apparatus|
|US8798228 *||Mar 1, 2012||Aug 5, 2014||General Electric Company||Method to reduce radiation dose delivered by imaging system|
|US8848860 *||Dec 20, 2011||Sep 30, 2014||Ge Medical Systems Global Technology Company, Llc||X-ray CT apparatus|
|US8961461||May 27, 2004||Feb 24, 2015||Baxter International Inc.||Multi-state alarm system for a medical pump|
|US8983024||Jul 29, 2011||Mar 17, 2015||William Beaumont Hospital||Tetrahedron beam computed tomography with multiple detectors and/or source arrays|
|US9025723 *||Mar 30, 2012||May 5, 2015||Koninklijke Philips N.V.||Pre-scan imaging with rotating gantry|
|US9107591 *||Oct 1, 2012||Aug 18, 2015||Koninklijke Philips N.V.||Interventional imaging and data processing|
|US9125572||Jun 22, 2012||Sep 8, 2015||University Of Utah Research Foundation||Grated collimation system for computed tomography|
|US9192786||May 24, 2007||Nov 24, 2015||William Beaumont Hospital||Real-time, on-line and offline treatment dose tracking and feedback process for volumetric image guided adaptive radiotherapy|
|US9198626 *||Jun 22, 2012||Dec 1, 2015||University Of Utah Research Foundation||Dynamic power control of computed tomography radiation source|
|US9320917||Dec 13, 2013||Apr 26, 2016||William Beaumont Hospital||Intensity modulated arc therapy with continuous coach rotation/shift and simultaneous cone beam imaging|
|US9326738||Jun 30, 2011||May 3, 2016||General Electric Company||Method and system for reduced dose X-ray imaging|
|US9332946||Jun 22, 2012||May 10, 2016||University Of Utah Research Foundation||Adaptive control of sampling frequency for computed tomography|
|US9339243||May 12, 2014||May 17, 2016||William Beaumont Hospital||Image guided radiotherapy with dual source and dual detector arrays tetrahedron beam computed tomography|
|US20020101960 *||Jan 4, 2002||Aug 1, 2002||Makoto Nokita||Radiographic apparatus, radiographic method, and computer-readable storage medium|
|US20020150210 *||Apr 12, 2002||Oct 17, 2002||Herman Stegehuis||Method, X-ray device and computer program for enhancing the image quality of images of the cardiovascular system of a patient|
|US20030043961 *||Aug 27, 2002||Mar 6, 2003||Tetsuya Horiuchi||X-ray CT system, gantry apparatus and operation console|
|US20030076919 *||Oct 3, 2002||Apr 24, 2003||Tatsuro Suzuki||X-ray computed tomography apparatus|
|US20030097062 *||Nov 21, 2001||May 22, 2003||Toth Thomas L.||System and method of medical imaging having default noise index override capability|
|US20030185343 *||Mar 25, 2003||Oct 2, 2003||Ge Yokogawa Medical Systems, Limited||Transmitted X-ray data acquisition system and X-ray computed tomography system|
|US20040017890 *||Jul 25, 2002||Jan 29, 2004||Arenson Jerome Stephen||Radiation exposure limiting scheme|
|US20040032928 *||Aug 16, 2002||Feb 19, 2004||Toth Thomas Louis||Method and system for implementing variable x-ray intensity modulation schemes for imaging systems|
|US20040101105 *||Nov 19, 2003||May 27, 2004||Koji Segawa||X-ray controlling method and X-ray imaging apparatus|
|US20040223585 *||Aug 21, 2002||Nov 11, 2004||Bjorn Heismann||Method for determining density distributions and atomic number distributions during radiographic examination methods|
|US20050031082 *||Jul 24, 2002||Feb 10, 2005||Haaga John R.||X-ray dose control based on patient size|
|US20050058249 *||Sep 11, 2003||Mar 17, 2005||Siemens Aktiengeselischaft||Method for controlling modulation of x-ray tube current using a single topogram|
|US20050089135 *||Jan 27, 2004||Apr 28, 2005||Toth Thomas L.||System and method of x-ray flux management control|
|US20050089136 *||Jan 27, 2004||Apr 28, 2005||Toth Thomas L.||System and method of determining a user-defined region-of-interest of an imaging subject for x-ray flux management control|
|US20050089137 *||Jan 27, 2004||Apr 28, 2005||Toth Thomas L.||System and method of collecting imaging subject positioning information for x-ray flux control|
|US20050089138 *||Jan 27, 2004||Apr 28, 2005||Toth Thomas L.||System and method of determining a center of mass of an imaging subject for x-ray flux management control|
|US20050089146 *||Oct 27, 2003||Apr 28, 2005||Toth Thomas L.||Method and apparatus of radiographic imaging with an energy beam tailored for a subject to be scanned|
|US20050185759 *||Feb 19, 2004||Aug 25, 2005||Toth Thomas L.||Method and apparatus to determine tube current modulation profile for radiographic imaging|
|US20050185760 *||Apr 18, 2005||Aug 25, 2005||Tatsuro Suzuki||X-ray computed tomography apparatus with x-ray intensity control|
|US20050267402 *||May 27, 2004||Dec 1, 2005||Janice Stewart||Multi-state alarm system for a medical pump|
|US20050277873 *||May 27, 2004||Dec 15, 2005||Janice Stewart||Identification information recognition system for a medical device|
|US20050277890 *||May 27, 2004||Dec 15, 2005||Janice Stewart||Medical device configuration based on recognition of identification information|
|US20060013358 *||Jul 12, 2005||Jan 19, 2006||Ge Medical Systems Global Technology Company, Llc||Scan program communication method and X-ray CT apparatus|
|US20060115039 *||Nov 30, 2005||Jun 1, 2006||Ge Medical Systems Global Technology Company, Llc||Dose evaluating method and X-ray CT apparatus|
|US20060198496 *||May 23, 2006||Sep 7, 2006||Toth Thomas L|
|US20060274877 *||Jun 6, 2006||Dec 7, 2006||Yasuhiro Noshi||Medical image display apparatus and medical image display system|
|US20060291612 *||Jun 20, 2006||Dec 28, 2006||Ge Medical Systems Global Technology Company, Llc||X-ray CT method and X-ray CT apparatus|
|US20060291614 *||Jun 26, 2006||Dec 28, 2006||Ge Medical Systems Global Technology Company, Llc||Radiographic apparatus|
|US20070025500 *||Jul 12, 2006||Feb 1, 2007||Ge Medical Systems Global Technology Company, Llc||Radiation tomography apparatus and scan condition setting device|
|US20070092058 *||May 28, 2004||Apr 26, 2007||Mattson Rodney A||Contour and scout scanning technique for pulsed x-ray large area ct detectors|
|US20070116337 *||Nov 23, 2005||May 24, 2007||Toth Thomas L||Method and system for automatically determining regions in a scanned object|
|US20070147577 *||Dec 20, 2006||Jun 28, 2007||Masaru Seto||Radiation tomographic imaging apparatus and radiation tomographic imaging method|
|US20070147579 *||Dec 23, 2005||Jun 28, 2007||De Man Bruno K B||Method and system for radiographic imaging with organ-based radiation profile prescription|
|US20070280408 *||Apr 12, 2007||Dec 6, 2007||Tiezhi Zhang||Scanning slot cone-beam computed tomography and scanning focus spot cone-beam computed tomography|
|US20070286332 *||Jun 4, 2007||Dec 13, 2007||Makoto Gohno||X-ray ct apparatus|
|US20080013689 *||Jul 31, 2007||Jan 17, 2008||Toth Thomas L|
|US20080031406 *||May 24, 2007||Feb 7, 2008||Di Yan||Real-time, on-line and offline treatment dose tracking and feedback process for volumetric image guided adaptive radiotherapy|
|US20080107231 *||Feb 27, 2006||May 8, 2008||Hitachi Medical Corporation||X-Ray Ct Apparatus|
|US20080152075 *||Jan 22, 2007||Jun 26, 2008||Paliwal Bhudatt R||Method and Apparatus for Low Dose Computed Tomography|
|US20090016484 *||Jun 20, 2008||Jan 15, 2009||Xueli Wang||Scanning detection device of an x-ray ct apparatus, an x-ray ct system and method of operation of the same|
|US20090168950 *||Dec 23, 2008||Jul 2, 2009||Jianying Li||X-ray ct apparatus and x-ray tube current determining method|
|US20090168951 *||Dec 23, 2008||Jul 2, 2009||Xiongwei Yan||Method for controlling x-ray exposure in x-ray ct system|
|US20090185655 *||Sep 23, 2005||Jul 23, 2009||Koninklijke Philips Electronics N.V.||Computed tomography method|
|US20090238330 *||Dec 5, 2005||Sep 24, 2009||Koninklijke Philips Electronics N.V.||Pulsed x-ray for continuous detector correction|
|US20100067647 *||Mar 18, 2010||Ali Bani-Hashemi||Dose-sparing tomographic imaging|
|US20100303196 *||Dec 2, 2010||Kabushiki Kaisha Toshiba||Voltage modulation in dual energy computed tomography|
|US20110002439 *||Jun 29, 2010||Jan 6, 2011||William Beaumont Hospital||Tetrahedron beam computed tomography|
|US20110091008 *||Jun 29, 2009||Apr 21, 2011||Koichi Hirokawa||X-ray ct apparatus|
|US20110110573 *||Jun 23, 2009||May 12, 2011||Koninklijke Philips Electronics N.V.||Image generation device with optimized dose control|
|US20120155605 *||Dec 20, 2011||Jun 21, 2012||Yujiro Yazaki||X-ray ct apparatus|
|US20120224665 *||Sep 6, 2012||Arun Kumar Chandrashekarappa||Method to reduce radiation dose delivered by imaging system|
|US20130044856 *||Feb 21, 2013||Koninklijke Philips Electronics N.V.||Interventional imaging and data processing|
|US20130343514 *||Jun 22, 2012||Dec 26, 2013||University Of Utah Research Foundation||Dynamic power control of computed tomography radiation source|
|US20140016740 *||Mar 30, 2012||Jan 16, 2014||Koninklijke Philips N.V.||Pre-scan imaging with rotating gantry|
|US20150078508 *||Sep 12, 2014||Mar 19, 2015||Samsung Electronics Co., Ltd.||Computed tomography apparatus and method of controlling x-ray by using the same|
|US20150146844 *||Nov 28, 2013||May 28, 2015||Toshiba Medical Systems Corporation||Method and system for spectral computed tomography (ct) with inner ring geometry|
|CN1302749C *||Dec 19, 2003||Mar 7, 2007||Ge医药系统环球科技公司||X-ray CT apparatus and computing method for exposure|
|CN1875886B||Jun 6, 2006||Dec 29, 2010||株式会社东芝;东芝医疗系统株式会社||Medical image display apparatus and medical image display system, and X ray computer tomography device|
|CN100500094C||Feb 21, 2005||Jun 17, 2009||Ge医疗系统环球技术有限公司||Method and apparatus to determine tube current modulation profile for radiographic imaging|
|CN100518649C||Jul 15, 2005||Jul 29, 2009||Ge医疗系统环球技术有限公司||Scan program communication method and X-ray CT apparatus|
|CN101816569B||Dec 24, 2004||Nov 14, 2012||Ge医疗系统环球技术有限公司||Radiation tomography system and tomography method|
|CN102512191B||Dec 28, 2007||Jul 23, 2014||Ge医疗系统环球技术有限公司||X-ray CT (Computed Tomography) device and method for determining current of X-ray tube|
|CN103298408A *||Apr 12, 2012||Sep 11, 2013||株式会社东芝||X-ray CT apparatus|
|CN103298408B *||Apr 12, 2012||Nov 25, 2015||株式会社东芝||X射线ct装置|
|CN103565460A *||Sep 26, 2013||Feb 12, 2014||沈阳东软医疗系统有限公司||Scan method and device capable of reducing scan dose|
|DE10309603B4 *||Mar 5, 2003||Mar 5, 2009||GE Medical Systems Global Technology Company, LLC, Waukesha||Röntgen-CT-Vorrichtung und Verfahren zu deren Steuerung|
|DE19527518B4 *||Jul 27, 1995||Jul 17, 2008||General Electric Co.||Röntgenröhren-Strommodulation während der Computertomographie-Abtastung|
|DE19806063C2 *||Feb 13, 1998||Sep 27, 2001||Siemens Ag||Verfahren zur adaptiven Reduzierung der Dosis in einem Röntgen-Computertomographie-System|
|DE19807639C2 *||Feb 23, 1998||Oct 31, 2001||Siemens Ag||Verfahren zur Modulation der Leistung einer Röntgenröhre eines Computertomographen (CT)|
|DE19933537B4 *||Jul 16, 1999||Mar 17, 2005||Siemens Ag||Röntgen-Computertomographie-Gerät mit Mitteln zur Modulation der Röntgenleistung einer Röntgenstrahlenquelle|
|DE19957083A1 *||Nov 28, 1999||Jun 21, 2001||Siemens Ag||Examination of periodically moving body part, heart using computer tomography unit|
|DE19957083B4 *||Nov 28, 1999||Nov 18, 2004||Siemens Ag||Verfahren zur Untersuchung eines eine periodische Bewegung ausführenden Körperbereichs|
|DE102014211150A1 *||Jun 11, 2014||Dec 17, 2015||Siemens Aktiengesellschaft||Verfahren zum Betreiben eines Computertomographen und Computertomograph|
|EP0747728A2 *||Apr 3, 1996||Dec 11, 1996||Adac Laboratories||Improved gamma camera imaging system|
|EP0819407A1 *||Jul 16, 1997||Jan 21, 1998||Ge Yokogawa Medical Systems, Ltd.||Fluoroscopy method and x-ray ct apparatus|
|EP0904732A1 *||Sep 30, 1998||Mar 31, 1999||Ge Yokogawa Medical Systems, Ltd.||X-Ray computed tomography method and apparatus|
|EP1103221A1 *||Nov 29, 2000||May 30, 2001||General Electric Company||Methods and apparatus for optimizing CT image quality with optimized data acquisition|
|EP1205768A2 *||Apr 3, 1996||May 15, 2002||ADAC Laboratories Inc.||Improved gamma camera imaging system|
|EP1304077A2 *||Oct 4, 2002||Apr 23, 2003||Kabushiki Kaisha Toshiba||X-ray computed tomography apparatus|
|EP1314397A2 *||Nov 21, 2002||May 28, 2003||GE Medical Systems Global Technology Company LLC||System and method of medical imaging having override capability|
|EP1348948A2 *||Mar 27, 2003||Oct 1, 2003||GE Medical Systems Global Technology Company LLC||Transmitted x-ray data acquisition system and x-ray computed tomography system|
|EP1389444A1 *||Aug 13, 2003||Feb 18, 2004||GE Medical Systems Global Technology Company LLC||Method and system for implementing variable x-ray intensity modulation schemes for imaging systems|
|EP1555938A2 *||Jun 20, 2003||Jul 27, 2005||CYRULNIK, Reuven, Avrahom||System and method for noninvasive diagnostic imaging, detection, and identification of substances by microwave/rf modulation of x-rays and applications in treatment of diseases characterized by the presence of pathological macromolecules or by the need for regeneration of normal tissue|
|EP1973469A2 *||Jan 22, 2007||Oct 1, 2008||Wisconsin Alumni Research Foundation||Method and apparatus for low dose computed tomography|
|EP1973469A4 *||Jan 22, 2007||Dec 30, 2009||Wisconsin Alumni Res Found||Method and apparatus for low dose computed tomography|
|WO1998033361A1 *||Jan 26, 1998||Jul 30, 1998||Picker Medical Systems, Ltd.||Variable current ct scanning|
|WO2003010555A2 *||Jul 24, 2002||Feb 6, 2003||Case Western Reserve University||X-ray dose control based on patient size|
|WO2003010555A3 *||Jul 24, 2002||Nov 27, 2003||Jeffrey L Duerk||X-ray dose control based on patient size|
|WO2003022016A2||Sep 5, 2001||Mar 13, 2003||Koninklijke Philips Electronics N.V.||Dose control in ct-images|
|WO2003022016A3 *||Sep 5, 2001||Oct 16, 2003||Ehud Dafni||Dose control in ct-images|
|WO2007084789A2||Jan 22, 2007||Jul 26, 2007||Wisconsin Alumni Research Foundation||Method and apparatus for low dose computed tomography|
|U.S. Classification||378/16, 378/108, 378/8|
|International Classification||H05G1/60, H05G1/26, A61B6/03|
|Cooperative Classification||A61B6/488, A61B6/542, A61B6/032, H05G1/26, H05G1/60|
|European Classification||A61B6/54D, A61B6/48N, A61B6/03B, H05G1/26, H05G1/60|
|Nov 19, 1993||AS||Assignment|
Owner name: GENERAL ELECTRIC COMPANY, WISCONSIN
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:TOTH, THOMAS LOUIS;REEL/FRAME:006780/0679
Effective date: 19931116
|Mar 26, 1998||FPAY||Fee payment|
Year of fee payment: 4
|Jul 2, 2002||FPAY||Fee payment|
Year of fee payment: 8
|Mar 27, 2006||FPAY||Fee payment|
Year of fee payment: 12